Quick timeline. December 2025, OpenAI said "there are no ads" after users spotted Peloton and Target promotions. February, ads officially launched. March, $100M annualized ad revenue with 600+ advertisers. August, expansion to 31 European markets. And now we learn the cross-site tracking infrastructure was running underneath all of it.
OpenAI labels __obi as an "analytics" cookie. Under GDPR — which applies across all 31 of those European markets — that classification determines what consent regime you fall under. A researcher asked OpenAI directly why a cookie that enables cross-site ad targeting is classified as analytics. OpenAI acknowledged the question but didn't answer it.
Google's cross-site tracking connects your browsing to search queries. Meta's connects it to your social graph. OpenAI's connects it to conversations where roughly 40 million people a day ask health questions — at 2 AM, about things they won't say out loud to anyone. Sam Altman has called "infinite, perfect memory" the strategic moat. That memory is now also ad inventory.
Safari's Intelligent Tracking Prevention blocks all third-party cookies, so __obi doesn't function on iOS browsers. If you're on Chrome, you're in the dataset.
Nine months from "there are no ads" to cross-site tracking across 31 countries.